From: Elena Reshetova <elena.reshetova@xxxxxxxxx>
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable qeth_reply.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: David Windsor <dwindsor@xxxxxxxxx>
Reviewed-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
[jwi: removed the WARN_ONs. Use CONFIG_REFCOUNT_FULL if you care.]
Signed-off-by: Julian Wiedmann <jwi@xxxxxxxxxxxxxxxxxx>
---
drivers/s390/net/qeth_core.h | 3 ++-
drivers/s390/net/qeth_core_main.c | 8 +++-----
2 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index badf42acbf95..f5ee62c98011 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -21,6 +21,7 @@
#include <linux/ethtool.h>
#include <linux/hashtable.h>
#include <linux/ip.h>
+#include <linux/refcount.h>
#include <net/ipv6.h>
#include <net/if_inet6.h>
@@ -632,7 +633,7 @@ struct qeth_reply {
int rc;
void *param;
struct qeth_card *card;
- atomic_t refcnt;
+ refcount_t refcnt;
};
struct qeth_card_blkt {
diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 6c815207f4f5..bc4e57540a9e 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -564,7 +564,7 @@ static struct qeth_reply *qeth_alloc_reply(struct qeth_card *card)
reply = kzalloc(sizeof(struct qeth_reply), GFP_ATOMIC);
if (reply) {
- atomic_set(&reply->refcnt, 1);
+ refcount_set(&reply->refcnt, 1);
atomic_set(&reply->received, 0);
reply->card = card;
}
@@ -573,14 +573,12 @@ static struct qeth_reply *qeth_alloc_reply(struct qeth_card *card)
static void qeth_get_reply(struct qeth_reply *reply)
{
- WARN_ON(atomic_read(&reply->refcnt) <= 0);
- atomic_inc(&reply->refcnt);
+ refcount_inc(&reply->refcnt);
}
static void qeth_put_reply(struct qeth_reply *reply)
{
- WARN_ON(atomic_read(&reply->refcnt) <= 0);
- if (atomic_dec_and_test(&reply->refcnt))
+ if (refcount_dec_and_test(&reply->refcnt))
kfree(reply);
}
--
2.13.5
--
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